The present invention relates to an apparatus and method for determining a characteristic of fuel (heavier gravity or lighter gravity fuel) supplied to a vehicular internal combustion engine.
U.S. patent application Ser. Nos. 08/041,588, now U.S. Pat. No. 5,363,314 issued on Nov. 8, 1994, No. 08/177,099 filed on Jan. 3, 1994, now U.S. Pat. No. 5,419,296, No. 08/325,665 filed on Oct. 19, 1994, and No. 08/408,007 filed on Mar. 22, 1995, exemplify previously proposed fuel characteristic determining apparatuses.
A Japanese Patent Application First Publication No. Heisei 3-271541 published on Dec. 3, 1991 exemplifies another previously proposed fuel characteristic determining apparatus.
In this Japanese Patent Application First Publication, a heavy or light gravity (quality) characteristic sensor for a fuel supplied to a vehicular internal combustion engine is provided in order to correct a fuel injection quantity supplied to the engine, i.e., ratio of an air-fuel mixture to be supplied to the engine. The fuel characteristic sensor includes a pair of electrodes installed in a fuel passage of the engine so that according to a variation in resistance in the fuel characteristic sensor between the pair of electrodes, the fuel characteristic, i.e., the heavier gravity fuel or lighter gravity fuel is detected. The heavier or lighter gravity is related to, specifically, a vaporization ability (vaporizability, vaporization percentage) that the fuel has. However, since, in the other previously proposed fuel supply quantity controlling apparatus disclosed in the latter Japanese Patent Application First Publication, the exclusively used (self-contained) fuel characteristic sensor is provided so that a whole system of controlling the air-fuel mixture ratio becomes expensive and a possibility of resulting in an erroneous determination of fuel characteristic becomes high due to a blending of an additive(s) in the fuel.